Figure 1.

Absorption spectrum of chromophores and water in the radiation therapy spectral range and visible to NIR spectral range. The optical window region where absorption of light due to physiological chromophores is low is shaded in pink. The absorption peaks of most commonly used photosensitizers for photodynamic therapy (PDT) are also depicted. Abbreviations: PpIX - Protoporphyrin IX, mTHPC - m-tetrahydroxyphenylchlorin, EtNBS - 5-ethylamino-9-diethylaminobenzo[α] phenothiazinium chloride, NPe6 - mono-L-aspartyl chlorin e6 and BPD - benzoporphyrin derivative monoacid A. HbO₂ - Oxygenated hemoglobin, Hb - Deoxygenated hemoglobin, H₂O - Water. Data adapted from Jacques et al ² and National Institute of Standards and Technology database.